There are many applications for an underwater tethered buoy in which it is essential for highly desirable to maintain the verticality of the buoy despite the existence of substantial currents. In underwater transponders, for example, it is desirable to keep the upward-looking transducer as nearly vertical as possible. Such underwater currents normally tend to cause the buoy to oscillate, tilt or rotate around its point of attachment to its tethering lead. One way of minimizing such departures from the vertical is to provide such strong flotation that the vertical component from lift is much greater than the horizontal component from the current. This effect can be further improved if the effective area exposed to the lateral forces can be minimized. Even when this is done, however, the solution is only partial since the best that can be accomplished is an attitude representing the resultant of the vertical and horizontal forces. Two specific problems which have been experienced with buoys of this type having a swept wing system as described herein, when placed in significant currents, are vortex sheeding from the buoy and the coupling between yaw and roll oscillations. The roll oscillation around the center of gravity of the buoy is excited by vortex shedding from each end 180.degree. out of phase from end to end. The lateral oscillation of the buoy and tether system around the anchor point on the ocean bottom appears also to contribute to roll oscillation.
It is therefore highly desirable to provide an arrangement where such underwater buoys can be maintained in a uniformly vertical attitude despite substantial variations in current. Thus, it may be desired to deploy such buoys in many locations with many different current conditions where there is little or no opportunity to make significant alterations in structure to assure verticality when anchored in location.